Process of making tubular metal walls.



W. M. FULTON. PROCESS OF MAKING TUBULAR METAL WALLS.

APPLICATION FILED JULY 22,1909.

Patented 00$. 4, 1910.

Wm; I

p U?- G @54 making fluids under pressure, and has for its object.elastic limit prurnn snares Parana ent re,

WESTON 1V1. FULTON, 0F KNOXVILLE, TENNESSEE,

ASSIG-NOR TO THE FULTON COM- PANY, 0F KNOXVILLE, TENNESSEE. ACORPORATION OF MAINE. V

Specification of Letters Patent.

PROCESS OF MAKING TUBULAR METAL WALLS.

Patentedfict. 4C, 191%..

Original application filed April 3, 1907, Serial No.'366,207. Dividedand this application filed July 22, 1909.

Serial No. 509,067.

To all whom it may concern:

, Be it known that I, WESTON M. FULTON, aresident of Knoxville,Tennessee, have invented a new and useful Improvement in the Process ofMaking Tubular Metal Walls, which invention is fully set forth in thefollowing specification.

This invention relates to processes of flexible corrugated metal wallsfor collapsible and expansible vessels, particularly of the classadapted for confining the production of corrugated metal walls of highresilience, of great strength and durability and which can be collapsedand expanded many times while confining fluids under pressure withoutmaterial injury to the wall.-

In my co-pending application, filed April 3, 1907, Ser. No. 366,207, ofwhich this application is a division, I have shown, described andclaimed the article herein, disclosed, and, therefore, do not claim thesame in this application.

Flexible tubular corrugated metal walls for collapsible and expansiblevessels are subject to repeated strains of tension and compression, ofvarying intensity in different portions of the metal composing thecorrugations, which in walls as heretofore made result in the occurrenceof cracks, particularly in the curved portions or bends, and also wherethe lateral portions of the corrugations merge into the curved portions.

Flexible corrugated tubular walls are usu-' ally made of copper,brass'or steel, and in order that these walls may be possessed offlexibility, advantage has heretofore been taken of the fact thatannealing imparts pliability to the metal of the corrugated wall, hence,in making corrugated walls where great flexibility is desired, as inthermosensitive or pressure-sensitive vessels, care is usually taken toavoid working temper into the metal during the formation of the wall andto remove any temper unavoidably formed therein bysubsequent annealingof the finished wall. It is well known that metals of the kind referredto, when in the annealed state, possess a very low consequently thestrains to which the corrugations of collapsible and expansible vesselsare subjected continuously, carry the metal beyond this elastic limit,particularly in the lateral portions near the bends, causing the metalto crystallize and crack, and thus destroy the wall. A furtherdisadvantage of employing annealed corrugated walls is that it detractsfrom the efliciency of the collapsible and expansible vessel and limitsits utility. Where such walls are used in vessels containing a liquidresponsive to slight changes in temperature, there is lost motion inthelateral portions of the corrugations which connect the curvedportions. This results from the pliable condition of the metal in theselateral portions which permits them to buckle in or out as the Vesselexpands or contracts, thereby detracting from the longitudinal movementof the walls of the vessel. This buckling of the lateral portionsthrows'more strain on the corrugations where they merge into the curvedportions, thereby contributing to the deterioration and ultimatefracture of the walls when the vessel is in operation.

To overcome the above objections and to secure the benefits of myinvention, I have devised a method of making flexible tubular metalwalls in which the metal at the bends is toughened and hardened inproportion to the strain sustained therein when the wall is inoperation, and in which the lateral portions of the corrugations joiningthe bends are strengthened and made resilient in the vicinity of thebends; said method consisting in taking a tubular metal wall and forcingportions of the tubular wall radially outward to form broad shallowcorrugations, leaving narrow uncorrugated connecting port-ions,deepening and narrowing said shallow corrugations and swaging inward thenarrow connecting portions by successive rolling operations, whichtoughen and harden the metal at the bends. while transferring portionsof the latter to the side or lateral portions of the corrugations tothere strengthen and render the wall resilient in proportion to therelative share of the strain sustained thereat when in operation.

The inventive idea involved is capable of expression in a variety ofmethods, one of which for the purpose of illustration is hereinafterspecifically described, and in the accompanying drawings I haveillustrated one of a flexible vessel showing the effects of pressure onthe lateral portions of the corrugations. Figs. 5 and 6 are views partlyin vertical section and partly in elevation, showing means forcorrugating a thin metal tube. Fig. 7 shows in central vertical sectionanother form of corrugated wall.

Referring first to Figs. 1, 2 and 3, I have therein shown the locationand direction of the principal strains which occur in the corrugationsof a flexible corrugated vessel when in operation, in order that mymethod may be better understood.

In Figs. 1 and 2, I have shown in plan and in central vertical sectionrespectively, a flexible corrugated cylindrical wall 1, having theportions connecting the bends in planes normal to the axis of theyessel. If a force be applied of sutficient amount to draw the walls ofthe vessel out till the corrugations disappear, there will result aplain uncorrugated cylinder having a diameter D which will be greaterthan the inner diameter and less than the outer diameter of the originalcorrugated cylinder. During this extension of the corrugated wall, themate rial in the disk portions 2, which is interior of or within thelines 4.4 of this plain cylinder is subject to tensile strains, whilethe material in portions 3 exterior to the lines 44 is subject tocompression or crushing strains. It may be here observed that radiallines in the fiat connecting'portions which join the bends tend torotate about an axis lying in the plane of the flat connecting or tionand intersecting the lines 44:. he direction of these attenuating andcompressing strains is clearly indicated in Fig. 3,

which shows a portion of a single corrugation much enlarged. In thedotted line position, the portions 5, 5 of the lateral Wall are in theirnormal position and subject to no strains. In the full line position,the portions 5, 5 are being opened outas the wall of the collapsiblevessel is extended. The material in the lateral ortion which liesinterior of the axial line t t, or nearer the axis of the vessel, isplaced under tension, as indicated by the-arrows 6, 6, while thematerial in the portion exterior'of the line 4 4, or nearer thecircumference of the vessel, is under compression, indicated by arrows7, 7.

When thewall is collapsed to its initial position with the lateralportions normal to the axis, the strains will be reversed. It will alsobe seen that during the collapsing from normal position to that wherethe bends contact with each other, strains of tension and compressionwill also occur; in fact, whenever the lateral portions are forced outof planes normal to the axis of the cylinder, these strains will appear,and their direction may be determined by noting the direction ofoscillation of the lateral portions with respect to their intersectionwith the lines'of the median cylinder. The'bends of the corrugations notonly participate in strains of attenuation and compression with thelateral portions, but also suffer bending strains as their radii ofcurvature shorten and lengthen during collapsing and extension. The resultant of these strains lie across the corrugations and are most activeat the points where the lateral portions merge into the curved portions.Contributory to the eflects of these last strains are those due tomovements of the lateral walls themselves .to bulge out to position 8When internal pressure is excessive, and to bulge in to position 9 whenexternal pressure predominates, as diagrammatically indicated in Fig. 4,where 1 designates a corrugated wall. The full line position shows thepressures balanced on the inside and outside, and the dotted linepositions indicate the lateral-walls bulged in or out where thepressures are greatest on the concave sides. i

It is to be further noted that fluid pressure within the cylindricalvessel sets up bursting strains of greater intensity in the outer setsof corrugations than in the inner corrugations nearer the axis, inproportion to the diameterof the wall. It is therefore essential toprovide for this difference of strain in the corrugations while makingthe wall.

With the above objects in view, my process results in the production andretention of resilience in the metal composing the wall,

and in so disposing the metal during the formation of the corrugationsas to intensify the'toughness and tensile strength of the wall at pointswhere the corrugations are subject to the greatest strains when in use.

In carrying out my invention I first form a tube of thin metal,preferably by bending the sheet into tubular form, and electricallybrazing the seam in the manner indicated in my U. S. Patents No. 853,351of May 14, 1907,and No. 916,140 of March 23, 1909. The resulting tube isthen well annealed by heatin it slowly to the annealing temperatureo themetal to rid the metal, as far as possible, of allstrains existingtherein, so that thedistribution of toughnessand resilience produced bythe subsequent steps of my process may not be offset or complicated birre larities in the originaltube wall. N ext, road circumferentialcorrugations are formed in the tube wall by forcing the metal radiallyoutward from the axis of the tube, preferably leaving at first narrowuncorrugated connecting portions bet-ween the broad corrugations. Thisstep of the process may be carried out by use of various mechanicalexpedients. I prefer to use rolls, and have shown a pair of such rollsin Fig. 5 suitable for the purpose, in which a die roll is looselymounted on a shaft 11 having a bearing in a stationary arm 12. Mountedabove the die roll 10, is a matrix roll-13 fast to a flexible powershaft 14, which permits of vertical adjustment by means of a hanger 15movable in guides 16. The matrix roll 13 is shown provided with acylindrical portion 17 which rolls on the perimeter of the tube to becorrugated. An expanding brace having two semi-circular members'18, 19,which when properly spaced apart by screws 20, to fit the interior ofthe tube, and positioned under the cylindrical portion 17, prevents theinward swaging of the tubular wall during the action of the rolls 10,13.

In operation, the upper or matrix roll is raised to clear the die roll.The expanding brace is inserted into the annealed tube 21 and expandedinto position near one end of the tube, leaving suiiicient amount oftube projecting beyond the brace to form the first corrugation at theend of the tube. .The tube is next passed over the die roll and underthe matrix roll either by hand or by mechanically operated means, tobring the end of the tube into corrugating position.

Matrix roll 13 is then lowered into contact with the tube, and pressedtoward the die roll 10, while the power shaft 11 is rotated. The metalof the wall is thereby pressed outwardly rom the axis of the tube into abroad circumferential corrugation. The brace within the tube preventsthe tube wall from being swaged inward as the corrugation is beingformed. The manner of mounting the corrugating rolls as above describedenables them to turn together irrespective of difference ofcircumference, die roll 10 being driven by friction against the tubewhich itself is caused to revolve by matrix roll 13. After the firstcorrugation is formed, the rolls are separated, the brace loosened andmoved along to allow for the next corrugation, and the corrugatingoperation repeated. The tube will now be provided with a series ofbroad, shallow, outwardly-extending corrugations 21 united by narrowuncorrugated portions 21". Rolls 10 and 13 are next replaced by narrowerrolls 22, 23, Fig. 6. The tube is again placed in corrugating position,the expanding brace being omitted, and each shallow corrugation isdeepened and narrowed by the action of the narrower rolls, and thesesteps are. re-

,is most advantageous.

peatedwith successive sets of rolls, till the requisite proportions havebeen reached for rendering the wall duly flexible. During this processof corrugating, the narrow uncorrugated connecting portions 21 areforced inward to form inwardly projecting corrugations, and may besomewhat narrowed, deepened and toughened by the swaging action of thenarrower flanges of the matrix roll, but I prefer to swage the innerprojecting corrugations much less in extent than the outwardly extendingcorrugations, as the inner corrugations do not need to be toughened tothe same extent as the outer corrugations, for the latter have tosustain the greater strains, as heretofore explained.

The successive narrowing and deepening of the corrugations gives to thewall resilience and toughness at those places where it Referringparticularly to Fig. 6, the curved portion of the narrowed corrugationincluded within the angle L is tempered and toughened more than thestraight portion connecting the in ner and outer curved portions, forthe reason that the pressure required in rolling the corrugation togreater depth is practically all exerted against this curved portion bythe die roll 23, while the straight portion is subjected only to themoderate action of friction between the sides of the die roll 23 and thematrix roll 22. Likewise, the inwardly curved portions 25 are alsotoughened and tempered more than the straight portions, because of theaction of the flanges of the matrix roll 22. When the corrugations ofthe second order are further narrowed and deepened, certaintoughenedportions I, K of the curved portion L will be carried over intothe lateral wall to form an extension of the straight portion, leaving aportion within the angle H to constitute the bend. This curved portion Hwill be in a similar manner further toughened and hardened by the actionof the die roll used to deepen and narrow the corrugation. As the resultof these operations, the corrugations will be toughened and maderesilient in the curved portions, and these qualities will be graduatedfor a considerable way into the lateral portions just where they needstrengthening.

Hence, this method of corrugating enables a corrugation to be made whichis most resilient at the curved portions where the greatest amount ofbending strains occur when the wall is in use; it also enablesresilience and strength to be gradually increased in its lat 'eral' wallproceeding in both directions toward the curved portions where itreaches a maximum, and where, as previously pointed out, the strains inthe corrugations reach their maximum efiect. Furthermore, the lateralwalls being toughened and tempered over a portion of their length asabove deprefer the process of rollin were narrowed and deepened byspinning them into female dies of successively narrower and deepershape, the spinning process thus applied, would produce the same resultas my rolling process, viz., it would impart resilience and toughness tothe corrugations and distribute same to desired points.

It is to be understood that the particular shape of the corrugations isnot an essential feature of my invention. While I prefer to form themsomewhat as indicated, the lateral walls thereof may be curved insteadofstraight, or they ma be. corrugated as described in my U. S. datedJune 2, 1903. Likewise, the inner and outer curved portions may have anyotherdesired shape, as for example, they may lie in a planeapproximately arallel with the axis of the wall, as indicate at 26, 26,Fig. 7.

I have shown the corrugations as lying in planes perpendicular to theaxis of the wall. I much prefer this method of arranging thecorrugations, but they may be made in the form of an ascending spiralsimilar to the threads of a screw or otherwise, without departing frommy invention.

The wall may be cylindrical or any other desired shape, as for example,elliptical in cross section. I

\Vhere the tube is made in the manner described in my Patents No.853,351 and No. 916,140 above referred to I prefer to anneal the sheetbefore the tube is formed, instead of annealing the tube-itsel It is tobe understood that it would be no departure from the spirit ofmyinvention to apply my process only in part. For example, 1f the tubewere annealed subsequent to the initial corrugating process, butprevione to the final narrowing and deepening process, the wall wouldevidently be only slightly inferior to mine, and would be a very decidedimprovement over walls made according to old processes. Or, if a wallwere made according to my process and then annealed at the conclusion ofsame, so as to deprive the wall of its resilience, it is evidentthatsuch a wall would still possess, to a very hi h degree, thetoughness and tensile strength imparted to it by my process, and

atent No. 729,926.

these would be distributed in the corruga gated metal walls, consistingin forming a thin walled tube, forcing the metal of the tube outwardfrom the axis of the tube to form broad corrugations therein with narrowuncorrugated portions connecting the broad corrugations, then deepeningand n ar- I, rowing said'corrugations while sub ect1ng the. metal. atthe bends to a metal rolling operation to toughen and temper the metalin said curved portions.

2. The process ofmaking flexible corrugated metal walls,consistingin'forming a' thin walled metal tube, forcing the metal of thewall outward to form broad corrugations, reducing the radius ofcurvature of the bends of said outwardly extending corrugations whiletransferring into the lateral portions, portions of said bends and.subjecting said curved portions to swaging pressure to toughen andtemper the metal in.

said curved portions. p

3. .The process of making flexible corrugated metal walls, consisting informing a thin walled metal tube, forcing the metal of the wall outwardto form broad corrugations, leaving narrow uncorrugated connectingportions between the outwardly extending corrugations, reducing theradius of curvature of the bends of said outwardly extendingcorrugations while transferring into the lateral portions, portions ofsaid bends, and forcing the metal in said narrow uncorrugated portionsinto inwardly projecting corrugations, and subjecting the curved p0r-'tions of said first-named bends to swaging pressure'to toughen andtemper the metal in said curved portions.

4. The process of making flexible corrugated metal walls, consisting informing a thin walled metal tube, annealing said tube, forcing'the metalof the wall outward to form broad corrugations, reducing the radius ofcurvature of the bends'of said outwardly-extending corrugations whiletransferring into'the lateral portions, portions of said bends, and'subjectlng said curved portions to swaging pressure to toughen andtemper thefmetal in said curved portions.

5. The process of making flexible corrugated metalwalls, consisting informing a thin walled metal tube, annealing said tube, forcing the metalof the wall outward to form broad corrugations, leaving narrowuncorrugated connecting portions between the outwardly extendingcorrugations, reducing the radius of curvature of the bends of saidoutwardly extending corrugations In testimonywhereof have signed thiswhile transferring into the lateral portions, specification in thepresence of two sub- 10 portions of said bends, and forcing the metalscribing witnesses.

in said narrow uncorrugated portions into inwardly projectingcorrugations, and sub- WESTON O j ecting the curved portions of saidbends to Witnesses:

swaging pressure to toughen and temper the MARY L. JONES, metal in saidcurved portions; HARRY O. MALLERY.

